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Monday is here one more time and the opportunity for science talk is here once again.  Time to brighten your day with selections from science sites across the globe.  New discoveries, new takes on old knowledge, and other bits of news are all available for the perusing in today's information world.  Today's tidbits include Earth-like planets are right next door, biodiversity helps protect nature against human impacts, X-rays reveal the uptake of nanoparticles by soybean crops, and first evidence that magnetism helps salmon find home.

Pull up that comfy chair and grab a spot near the fire.  There is always plenty of room for everyone.  Another session of Dr. Possum's science education, entertainment, and potluck discussion is set to begin.

Featured Stories
New information shows six percent of red dwarf stars have Earth-like planets so the closest of those may be only 13 light-years away (nearby in astronomical terms).

Red dwarf stars are smaller, cooler, and fainter than our Sun. An average red dwarf is only one-third as large and one-thousandth as bright as the Sun. From Earth, no red dwarf is visible to the naked eye.

Despite their dimness, these stars are good places to look for Earth-like planets. Red dwarfs make up three out of every four stars in our galaxy for a total of at least 75 billion. The signal of a transiting planet is larger since the star itself is smaller, so an Earth-sized world blocks more of the star's disk. And since a planet has to orbit a cool star closer in order to be in the habitable zone, it's more likely to transit from our point of view.

As human and nature continue to interact in various ways biodiversity serves to protect the natural environment.

Unlike other scientists usually relying on short-term, artificial study plots, the researchers studied long-standing pasture grasslands on southern Vancouver Island for 10 years. The 10-hectare site owned by the Nature Conservancy of Canada consists of oak savannah where fires have been suppressed for about 150 years.

The team selectively burned plots to compare areas of mostly grasses with areas of mixed grasses and diverse native plants.

They found that seemingly stable grassland plots collapsed in one growing season and were subsequently invaded by trees. More diverse sites resisted woody plant invasion.

Diversity also affected fire itself. More diverse areas had less persistent ground litter, making high-intensity fires less likely to recur than in single-species grasslands with more litter serving as fuel.

With the increasing use of nanoparticles in various manufacturing processes concern for human exposure is rising with evidence of particle absorption by soybean crops.
Nanoparticles are present everywhere, for example in the fine dust of wood fires. Even a simple chemical compound behaves differently as a nanoparticle, mostly due to the increased specific surface area and reactivity. These appealing properties are why so-called Engineered Nanoparticles (ENPs) are now widely used in industrial processing and consumer goods. At the same time, their high reactivity has raised concerns about their fate, transport and toxicity in the environment.

...

Cerium was shown to be present not only in the nodules close to the soil but had also reached the plant pods.  A detailed spectral analysis of the X-ray signals showed that the cerium in the nodules and pods was in the same chemical state as in the nanoparticles. However, part of the cerium had changed its oxidation state from Ce(IV) to Ce(III) which can alter the chemical reactivity of the nanoparticles.
Cerium nanoparticle in soybean    

Zinc was detected in nodules, stems and pods in concentrations higher than in a control group of plants. The spectral analysis did not show the presence of zinc in the plants bound as ZnO nanoparticles which means that the zinc in the nanoparticles had been biotransformed. The spectra suggest that organic acids present in the plants such as citrate, are the probable ligands for the zinc.

Scientists have long wondered how sockeye salmon swim thousands of miles into the ocean and then years later find the way home to their river of birth.
A new study, published in this week's issue of Current Biology and partly funded by the National Science Foundation, suggests that salmon find their home rivers by sensing the rivers' unique magnetic signature.

...

Results from this study showed that the intensity of the magnetic field largely predicted which route the salmon used to detour around Vancouver Island; in any given year, the salmon were more likely to take whichever route had a magnetic signature that most closely matched that of the Fraser River years before, when the salmon initially swam from the river into the Pacific Ocean.

Knucklehead's Photo of the Week
Yellow Tang with Cleaner Wrasse
Above Green Bubble Coral

TANG WRASSE work sheet DSCN1970

©Knucklehead, all rights reserved, presented by permission.  (Click on the image to see more in the same series.)

Other Worthy Stories of the Week
Hubble catches the moment when the lights went out
Cassini sees Titan cooking up smog
Massive stellar winds are made of tiny pieces
3-D printing breakthrough with human embryonic stem cells
Shimmering water reveal cold volcanic vent in Antarctic waters
Water purification on the cheap
A spiral galaxy with a secret
Mercury contamination in water can be detected with a mobile phone
The wings of the seagull nebula
Obsidian lava flows in the cascades and long valley
Largest prime number to date found
Eastern Europe was an important pathway in evolution
Motor memory: How we learn to move
3-D printing on the micrometer scale
Scientists study Antarctic ice cores for clues to why Earth emerged from the Ice Age
Shining light on the mystery of Picasso's paints

For even more science news:
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BBC News Science and Environment
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LiveScience
New Scientist
PhysOrg.com
SciDev.net
Science/AAAS
Science Alert
Science Centric
Science Daily
Scientific American
Space Daily

Blogs:
All-GeoGeology and Earth science
Cantauri Dreams space exploration
Coctail Party Physics Physics with a twist.
Deep Sea News marine biology
List of Geoscience Blogs
Science20.com
ScienceBlogs
Space Review
Science Insider
Scientific Blogging.
Space.com
Techonology Review
Tetrapod Zoology vertebrate paleontology
Wired News
Science RSS Feed: Medworm
The Skeptics Guide to the Universe--a combination of hard science and debunking crap

At Daily Kos:
This Week in Science by DarkSyde
Overnight News Digest:Science Saturday by Neon Vincent. OND tech Thursday by rfall.
All diaries with the DK GreenRoots Tag.
Astro Kos
SciTech at Dkos.

NASA picture of the day. For more see the NASA image gallery or the Astronomy Picture of the Day Archive
 photo OrionNebula_zps2f229ab0.jpg
Orion Nebula viewed in infrared, NASA, public domain

Originally posted to possum on Mon Feb 11, 2013 at 12:30 PM PST.

Also republished by SciTech.

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